There is a continually increasing demand for devices capable of storing more energy per unit volume (Wh/l) or energy per unit mass (Wh/kg) than today's premier rechargeable Li-ion batteries. One increasingly sought after route to meeting this demand is to utilize divalent magnesium (Mg2+), rather than the monovalent cation lithium (Li+) because magnesium enables nearly twice as much charge to be transferred, per weight or volume, than Li+ thus enabling high energy density. Furthermore the abundance of Mg metal and readily available compounds containing Mg can enable significant cost reduction relative to Li-ion batteries.